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How to clean-up scanned sketch?


M

michaelvs

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Hi there!

Can anyone recommend me how to clean up a scanned sketch? As a result I need to have a line art (only black lines) with a transparent background.

I was trying to use levels and then "select by range" command to select background and then invert selection and stroke it. The problem is that it's hard to select the background in my case.

Here is how my sketch looks like, see attached

Thank you

Michael
 

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Your background makes this virtually impossible to pull out a clean black outline, by any means I know. Channel selection will help, but you'll still have lots of noisy grey or color artifact to deal with. In order to use that method successfully, you really need to have clear lineart, black on white. What you have is mud with darker mud, sorry to say but that is the main problem. I played with it using 4 different adjustments to get rid of the noisy BG. I imagine there are others on the forum with better skills, knowledge, and ideas.

But the issue is, like in taking a photograph, the work you do to post processing and the success you have are very very dependent on the quality of the photo itself. Can you go back and scan it at higher resolution, set your contrast as high as possible? Did you scan this as black and white? That may help.

The first thing I thought of when I saw this particular image was that you could easily reproduce it in Photoshop using the pen tool, tracing over your original lines. That may be your best bet, IMHO.

OTOH, if you're going to be a real artist, stop drawing on brown wrapping paper and buy some decent rag sketch pads, even newsprint would be better than this! That's why they came up with the term "starving artist" -- all your resources support your art and you eat beans and rice (and eat at mom's) for the first 20 years of your career!

No chit mon. :rofl:

cleanup.PNG

A black and white adjustment layer helped some, set to maximum black, but like I said, you're dealing with a difficult contrast situation.

cleanup.PNG
 
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ibclare said:
Your background makes this virtually impossible to pull out a clean black outline, by any means I know. Channel selection will help, but you'll still have lots of noisy grey or color artifact to deal with.
Click to expand...
Thank you for the advice, the problem is that this I got this sketch from an artist (as a first step of some illustration for an initial review). So what I am trying to do it is to make a line art out of it and then compare against the reference image.I was thinking maybe some filters can help me? Find Edges or something?I do have it with a higher resolution but I dont think it will help, see attached. and this is actually a photo but not a scan
 

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"...The first thing I thought of when I saw this particular image was that you could easily reproduce it in Photoshop using the pen tool, tracing over your original lines. That may be your best bet, IMHO..."

I agree completely with Clare! Manual tracing is your best option.

The signal to noise ratio is just too bad to get enough improvement from any filter that I have ever used, including multiple filter combinations such as "reduce noise" followed by "find edges".

Tom M
 
I don't need to make it perfect. Since I need it only to compare with a reference image... I just need to have visible/thick lines so I can overlay it above the photo and see the difference.
 
"I don't need to make it perfect. Since I need it only to compare with a reference image... I just need to have visible/thick lines so I can overlay it above the photo and see the difference."

Clare's suggestion to use the pen tool will do exactly what you described in the text quoted above, and do so with very little effort. If you aren't completely comfortable with the pen tool, it's really a good tool to learn.

Tom
 
LOL, yeah, Tom, I tried that: reduce noise had no effect, no matter what combo of settings I tried. Blend if, multiple options, forget it. Find edges? What edges? They're lost. There is no contrast in tonality whatsoever between the grey lines and the beige background. They can't be separated by PS. I imagine if you were to go to CSI:NY or NCIS and ask Abbie, you might get some virtual help! Sorry, couldn't resist. Tom is one of our best tech members. If he can't see a solution other than tracing . . .

You could I suppose, take the last step I created, then use the process in Inkz's video tutorial to make as much transparency as possible. You could select everything, go to select>modify>expand, then fill the selection. But you would be filling all the artifact. If you just want a very very rough transparency, you will get something like that but you will have to manually erase a lot of junk to see through it. It would be much less time consuming to trace it.
 
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Great idea AM! If the OP doesn't feel comfortable with the pen tool, for something like this, the brush or pencil tool will work almost as well.

Tom M
 
Lowered lighting to get a better look at the lines, looks like a boat in any harbour or even a canal barge in the cut, redrawn over the lines available with pen tool.

Poor drawing/sketch worsened by poor scan copy?

pentool.gif before and after.
 
And, to show how one can get exactly what you asked for using the pen tool, I took Paul's intentionally low-rez, but nicely done version and converted it to a PNG with black lines and a transparent background.

T
 

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I used the Line Tool for all the straight lines with a weight of 0.05 cm. It will make a new layer for each line. When your done with the lines just merge the layers. (or shift + option + command + E, group originals)

Screen Shot_01.png

The Pen Tool set to path > STROKE PATH > uncheck simulate pressure. For the curves.
And the Ellipse Tool for the round parts.

sketch_02.jpg

Just a different way to do it.
 
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As we have been suggesting . . . Line tool, pencil tool, brush, pen; any combination of the above. But tracing over is the best solution as you guys have demonstrated. Good examples Paul and IamSam.
 
Ok, I see, I probably need to trace it over with a pen tool. The thing is that I have a bunch of sketches like this and I need to be able to compare each of them against a reference image.
Anyway, thank you so much for helping me with this!
 
michaelvs said:
Paul, this is very close to what I need. Could you explain to me how you did this? Did you trace it over manually or used some adjustment?

Thanks,i
M
Click to expand...


Just lowered the lighting of original image made a new blank layer over the top and used the pen tool to draw all of the lines in, i set the brush tool at 3 pixels and one pixel for the thinner lines, the circle was with the ellipse tool and then stroked circle.
 

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